One of my R2's has a problem. It randomly, once or twice a week, just stops printing. As far as I can see only three things are in this path. The Raspberry Pi, the flash card, and the system board. In my case the system board is and Arduino Mega Ramps. I have started by swapping out the Pi, if within a week I have a failure I will swap out another component. Has anyone else had this problem? If so what part was the failing part? Is there a recommended flash card because it sure seems that this could be the failure.